UNITED NATIONS, Feb 19 (Reuters) - The U.N. Security Council will likely vote on a draft resolution to boost humanitarian aid access in war-torn Syria on Friday, diplomats said, but it was unclear if Russia and China would support or veto the Western- and Arab-backed text.

Australia, Jordan and Luxembourg finalised the draft on Wednesday, which includes demands for cross-border aid access, an end to shelling and aerial bombardment - including barrel bombs - and threatens "further steps" in the event of non-compliance.

These were among the main sticking points during almost two weeks of negotiations. Western diplomats said it was unclear if Moscow and Beijing - two of the five veto-wielding powers on the 15-member council - would support or block the resolution.

Russia, supported by China, has shielded Syria on the U.N. Security Council during the three-year-long civil war. They have vetoed three resolutions condemning Syria's government and threatening it with possible sanctions.

"Of course the decision will be taken in Moscow," said a U.N. diplomat, speaking on condition of anonymity. "It does remain uncertain but, objectively, nothing in this humanitarian text should be unacceptable for any delegation."

Russian Foreign Minister Sergei Lavrov said on Monday Russia would block the adoption of a resolution that allowed aid convoys to enter Syria without the consent of the Damascus government. He also warned earlier on Wednesday that the draft resolution should not be "politicized."

"If nobody in the Security Council seeks to politicize this issue, to promote one-sided approaches, I am convinced we will be able to reach an agreement in the coming days," Lavrov told a Gulf states meeting in Kuwait, Interfax news agency reported.

Chinese Foreign Ministry spokeswoman Hua Chunying said China was actively participating in the process of producing a resolution.

"We believe that, in the current circumstances, the action by the Security Council should be conducive to pushing for a political solution to the Syria problem," she told reporters in Beijing.

"The relevant action should also respect the U.N.'s guiding principles on humanitarian aid, upholding fairness and neutrality."

FRUSTRATION

Russia initially dismissed the draft resolution as an unjust bid to blame Damascus for the conflict and the aid crisis in Syria, where the United Nations say 9.3 million people need help.

But Moscow then proposed a rival text and Australia, Jordan and Luxembourg wrapped some of those suggestions into their draft. While Russia then engaged in negotiations, Western diplomats said progress on the text had stalled.

"We're not making progress by just meeting and meeting and meeting, so we're going to push it to a vote," said a senior U.N. diplomat, speaking on condition of anonymity.

Western members of the Security Council have been considering a humanitarian resolution for almost a year. After months of talks, the council eventually adopted a non-binding statement on Oct. 2 urging more access to aid, but that statement only produced a little administrative progress.

U.N. aid chief Valerie Amos last week urged the U.N. Security Council to act to increase humanitarian access in Syria. Amos has repeatedly expressed frustration that violence and red tape have slowed aid deliveries to a trickle.

The United Nations has said that well over 100,000 people have been killed in the civil war. The opposition Syrian Observatory for Human Rights has said that more than 136,000 have been killed since a revolt against President Bashar al-Assad began in March 2011. (Additional reporting by Gabriela Baczynska, and Sui-Lee Wee in BEIJING; Editing by Mark Heinrich, Jonathan Oatis, Paul Tait and Ron Popeski)